None.
The present invention relates to temperature sensors, and more particularly, to temperature sensor probes having a metallic sheath and which can be readily attached relative to a wall structure. The present invention relates both to the structure and to the method of making such temperature sensors probes.
Numerous temperature sensor structures are known in the prior art. One simple type of temperature sensor is a thermocouple, wherein two dissimilar metals are joined together, typically at the end of wires of each of the types of metal, so that an electrical voltage is generated between the points of contact as a function of the temperature sensed. A second type of temperature sensitive element is a xe2x80x9cthermistorxe2x80x9d, having an element whose electrical resistance changes as a function of temperature. Other types of temperature sensitive elements are also known in the art.
Often it is desired to extend the temperature sensitive element into a fluid flow, such as into the center of an air flow duct, into the center of a liquid flow pipe, into a wind or from a moving vehicle. The support structure for the temperature sensitive element should disrupt the flow as little as possible, but must be strong enough to withstand the drag of the flow. A metallic sheath is a common component of temperature probes used to support the temperature sensitive element. Sheathed temperature probes commonly include a long, thin cylindrical metallic sheath which houses the temperature sensitive element and extends into the flow. Common sheathed temperature probes include lengths ranging from about 2 xc2xd to 12 inches and outer diameters ranging from about xe2x85x9 to xe2x85x9c of an inch.
Often it is desired to attach the sheathed temperature probe to a wall or other support structure. The cylindrical sheath does not facilitate attachment, so it has been common to attach a flange extending normal to the sheath. The flange must securely attach to the sheath and durably support moments placed on the sheath by the fluid flow. The flange should facilitate attachment to the support wall, such as with fastener openings.
As the temperature probe industry matures and temperature probes are designed into more and more applications, the cost of temperature probes has declined. At the same time, further cost reductions will allow temperature probes to be designed into additional applications. The cost of the flange and the attachment method adds significant costs to the temperature probe assembly. Added costs become more significant as the overall price of temperature probes declines. A less costly and more durable structure and method is needed for flanged and sheathed temperature probes.
The present invention is a sheathed and flanged temperature probe formed using a cylindrical sheath and a flange of the same metallic material. The cylindrical sheath has a length at least an order of magnitude greater than its outer diameter. The temperature sensing element is contained within the sheath, with electrical leads protruding from the open end of the sheath. The flange member is formed from a single piece of metal, cold drawn using an awl to form a continuous sleeve having an axis perpendicular to the planar surface of the flange. The sheath is inserted into the sleeve. The flange is secured to the sheath solely using a press crimper, pressing inward over a majority of the circumference of the sleeve, leaving crimp edges extending on opposite sides of the sleeve. In a preferred embodiment, at least one planar surface of the flange may be sealed with a gasket.
By using the same material for the flange and the sheath, the materials share the same coefficient of expansion. The attachment will not be compromised by changes in temperature. Further, the crimp attachment is more durable than prior art attachments. The entire assembly process costs much less, takes less time, and involves fewer parts.